Pipes base on polyolefin resin for manufacturing pipelines and couplings for assembling them

Abstract

Pipes and couplings for manufacturing pipelines comprising a wall having at least one layer of core material consisting essentially of a crosslinked polyolefin resin and at least one layer of surface material consisting essentially of a thermoplastic resin, said core material being crosslinked to a rate higher than 30%.

We claim: 
     
       1. Pipes for manufacturing pipelines of great length by end-to-end assembly, comprising a wall having at least one layer of core material consisting essentially of a crosslinked polyolefin resin and at least one layer of surface material consisting essentially of a thermoplastic resin, said core material being crosslinked to a rate higher than 30%. 
     
     
       2. The pipes of claim 1, wherein the said crosslinked core material is obtained by crosslinking in a humid atmosphere a composition based on a polyolefin resin grated by a reaction with a monomer containing at least one hydrolyzable group to give rise to condensation reactions. 
     
     
       3. The pipes of claim 1 or 2, wherein the said layer of surface material is present on the outside of the said pipes, forming an envelope around the said crosslinked core material. 
     
     
       4. The pipes of claim 1 or 2, wherein said pipes are prepared by coextrusion of the core and of the surface material layers before crosslinking of the polyolefin resin forming the core material. 
     
     
       5. The pipes of claim 1 or 2 wherein they comprise two layers of surface material disposed on the inner face and the outer face of the tubular core respectively. 
     
     
       6. Tubular couplings for the assembly of the pipes of claim 3, wherein said couplings comprise at least one layer of core material analogous to that of the pipes of claim 3 and a layer of surface materials analogous to that of the pipes of claim 3, suitable for being welded to the latter by welding means. 
     
     
       7. Couplings in accordance with claim 6, wherein welding means are formed by an electrical heating resistor embedded in the said couplings. 
     
     
       8. Couplings in accordance with claim 6, wherein they comprise an annular crown forming a radial extension of the said layer of surface material in a median zone of the coupling for being intercalated between the ends of two consecutive pipes disposed end to end for assembly by means of the said coupling. 
     
     
       9. The pipes of claim 1 or 2 wherein said core material consists essentially of a crosslinked polyethylene or a crosslinked polypropylene and said surface material consists essentially of a thermoplastic polyethylene or a thermoplastic polypropylene.